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abbott287
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Which is just imagined. Not real.jbriggs444 said:That turns out not to be the case. One can describe a notional rubber band without requiring that it be embedded in a higher dimensional space, infinite or not.
Which is just imagined. Not real.jbriggs444 said:That turns out not to be the case. One can describe a notional rubber band without requiring that it be embedded in a higher dimensional space, infinite or not.
How do you know it's not real?abbott287 said:Which is just imagined. Not real.
Says who? I think it may be your imagination that is lacking; the math has no trouble describing it, despite your suggestion that it can't.abbott287 said:Which is just imagined. Not real.
abbott287 said:Define infinite.
Yes, it didnt started with a point. Big bang started with a singularity.abbott287 said:You seem to be contradicting yourself. You said do not think of it as a point, which is how I think of it.
You can read the previous discussions for the answer, which I was also confused at that time.abbott287 said:Then you told me the distance beteeen points was zero, which makes everything a point!
There was nothing before the big bang.abbott287 said:Then if the big bang happened everywhere, there was a lot of something there pre big bang!
You have to stop as thinking about the universe as being embedded in some containing [three dimensional?] space. It does not need to be embedded in anything.gary350 said:If the universe is not infinite that means is stops somewhere. If the universe stops then what is on the other side of that? It is beyond comprehension that the universe stops or is infinite.
One problem with saying that something is beyond comprehension is that it is an excuse to stop thinking or learning.gary350 said:If the universe is not infinite that means is stops somewhere. If the universe stops then what is on the other side of the universe? It is beyond comprehension that the universe stops or is infinite.
I had started to write almost exactly this, citing Einstein's famous dislike of quantum mechanics as an example.PeroK said:These questions in contrast could be an excuse to start thinking and learning.
gary350 said:If the universe is not infinite that means...
Why does it need to have had a first state? What is the smallest strictly positive real number?Sue Rich said:The theory is that our universe started with the Big Bang. You're now saying it's possible the entire universe could have started infinite. If so. then how was the infinite universe started?
The Big Bang theory can't rewind things all the way back to ##t=0##. The maths breaks down. In particular there is no consistent way to get from a point to our universe, infinite or otherwise. No one knows how it started.Sue Rich said:The theory is that our universe started with the Big Bang. You're now saying it's possible the entire universe could have started infinite. If so. then how was the infinite universe started?
With the Big Bang.Sue Rich said:The theory is that our universe started with the Big Bang. You're now saying it's possible the entire universe could have started infinite. If so. then how was the infinite universe started?
Counterexample: The surface (!) of Earth is not infinite, but it doesn't stop somewhere.gary350 said:f the universe is not infinite that means is stops somewhere.
Sue Rich said:The theory is that our universe started with the Big Bang. You're now saying it's possible the entire universe could have started infinite. If so. then how was the infinite universe started?
You probably are imagining the Big Bang as starting with a single point at t=0. The truth is, the point at t=0 is not a valid point in the theory. It is an extrapolation to a region where the math no longer makes any sense.Sue Rich said:The theory is that our universe started with the Big Bang. You're now saying it's possible the entire universe could have started infinite. If so. then how was the infinite universe started?
Sue Rich said:The theory is that our universe started with the Big Bang. You're now saying it's possible the entire universe could have started infinite. If so. then how was the infinite universe started?
There has to be something if its expanding. It can't expand into something that's not there.jbriggs444 said:You have to stop as thinking about the universe as being embedded in some containing [three dimensional?] space. It does not need to be embedded in anything.
mfb said:With the Big Bang.
Note that a possible singularity, no matter if we had one or not, is not part of the Big Bang.
Counterexample: The surface (!) of Earth is not infinite, but it doesn't stop somewhere.
abbott287 said:Then define singularity. You cant. Its a word meaning we don't know.
The Earth is round. So you have a start point and an end point. Then you just start over again. If the universe is looped, why don't we see things coming back at us from the past, just like we would see someone walking back around to the starting point on the round earth. Infinities don't work, and they do work, depending on how you view them. Ex: There were an infinite amount of days before I was born, so I could never have been born. Ex:2. Yes there were an infinite amount of days, but you were born on one of them... Both examples can be right or wrong, depending on how you look at it. Thats the paradox of infinite. Black holes are not crushed out of existence, or we would see no signs of them hanging around. If they exist, the crushing seems to have stopped at some point.
It doesn't have to expand into anything. Expansion refers to metric expansion, which relates to the changing distances between points in space.abbott287 said:There has to be something if its expanding. It can't expand into something that's not there.
abbott287 said:You seem to be contradicting yourself. You said do not think of it as a point, which is how I think of it.
abbott287 said:There has to be something if its expanding. It can't expand into something that's not there.
abbott287 said:Then define singularity. You cant. Its a word meaning we don't know.
abbott287 said:Then define singularity. You cant. Its a word meaning we don't know.
abbott287 said:There has to be something if its expanding. It can't expand into something that's not there.
do
abbott287 posts a misconception
PF corrects it
while universe <> heat death
Not only. Zero spatial curvature is also consistent with a 3-torus which is finite in size.dreens said:This is a space that is finite, three dimensional, and a valid manifold. If you travel far enough in any direction you return to your start point.
My understanding is that if our universe were like this, there ought to be measurable curvature. This would manifest somehow in cosmological observations, but currently the measured curvature of the universe is consistent with zero. Zero curvature is consistent with the FRW metric, an infinite and flat manifold expanding over time as discussed at length above.
It's not a matter of how you look at it. You are trying to use logic to answer a question that can't be answered by logic. Logical deduction requires you to start from certain assumptions or axioms. It doesn't help if we don't know all the laws of the universe. Probability fails when you have an infinite event space. That doesn't mean that it's impossible to have an infinite event space.abbott287 said:Ex: There were an infinite amount of days before I was born, so I could never have been born. Ex:2. Yes there were an infinite amount of days, but you were born on one of them... Both examples can be right or wrong, depending on how you look at it.
timmdeeg said:Not only. Zero spatial curvature is also consistent with a 3-torus which is finite in size.
Interestingly Steiner has claimed that a torus "gave the best match" to the WMAP data.dreens said:Agreed. That’s a more obvious way to get a finite, uncurved, 3D space. Especially if you think of a 3-torus as a cube with opposite sides identified, so that if you go through the right you appear on the left, etc.
Does anyone know how well this possibility is excluded by astrophysical observations?
timmdeeg said:Interestingly Steiner has claimed that a torus "gave the best match" to the WMAP data.
https://www.nature.com/news/2008/080523/full/news.2008.854.html
mfb said:“Gives the best match” is not a good argument if you compare an easy model to one with 6 (?) free parameters more.